Roll assist mechanism for tarp systems

Abstract

In a tarp system used to cover an open container such as a truck, the tarp being connected on one longitudinal edge to a roll bar, an improved mechanism for assisting movement of the roll bar comprises one or more constant force springs, each spring attached at one end to a longitudinal side of the container and at the other end to a reel mounted on the roll bar. When the roll bar is at one side of the container, the tarp is rolled around the roll bar and the constant force springs are extended. As the bar rolls across to the opposite side, the tarp is unrolled to cover the container opening, and the constant force springs wind into a coil around the reel.

What is claimed is:  
     
       1. A roll tarp system for an open top vehicle or container, the system comprising: 
       a roll bar;  
       a flexible material having dimensions approximately matching the dimensions of the open top, the flexible material having first and second longitudinal edges, the flexible material attached along one longitudinal edge to the vehicle or container and along the other longitudinal edge to the roll bar;  
       a reel fixedly attached to the roll bar;  
       a constant force spring having a first end fixed to said reel such that the spring is windable thereon, and having a second end mounted to the vehicle or container;  
       whereby rolling of the roll bar in one direction winds the spring onto the reel and rolling the roll bar in the other direction unwinds the spring from the reel.  
     
     
       2. The roll tarp system of  claim 1  wherein the roll bar has two ends, and further comprising an electric motor at one end. 
     
     
       3. The roll tarp system of  claim 2  wherein the reel is located near the end of the roll bar where the electric motor is located. 
     
     
       4. The roll tarp system of  claim 3  further comprising: 
       a second reel, the second reel being located near the end of the roll bar opposite where the electric motor is located; and,  
       a second constant force spring having two ends, one end attached to the second reel and the other attached to the vehicle or container.  
     
     
       5. The roll tarp system of  claim 4  further comprising: 
       a third reel, the third reel located near the end of the roll bar where the electric motor is located; and,  
       a third constant force spring having two ends, one end attached to the third reel and the other attached to the vehicle or container.  
     
     
       6. The roll tarp system of  claim 5  further comprising means for pivotably mounting an end of at least one of the springs to the vehicle or container. 
     
     
       7. The roll tarp system of  claim 6  wherein said means comprises a hinge. 
     
     
       8. A roll tarp system for an open top vehicle or container, the opening having longitudinal and widthwise dimensions and edges at its perimeter, the system comprising: 
       a roll bar having first and second ends;  
       a flexible material having longitudinal and widthwise dimensions approximately matching the dimensions of the open top, the flexible material attached along one longitudinal edge near to a longitudinal edge of the opening, the flexible material being attached along its opposite longitudinal edge to the roll bar;  
       means for rolling the roll bar attached to the first end of the roll bar;  
       a reel attached to the roll bar; and,  
       a constant force spring adapted for winding on the reel, the spring having length approximately matching the widthwise dimension of the opening, the spring being attached at one end to the reel, and the spring being mounted at the other end to the vehicle or container;  
       whereby rolling the roll bar in one direction will wind the spring on the reel while unwinding the flexible material from the roll bar, and rolling of the roll bar in the opposite direction will unwind the spring from the reel while winding the flexible material onto the roll bar.  
     
     
       9. The roll tarp system of  claim 8  wherein the means for rolling the roll bar is a crank. 
     
     
       10. The roll tarp system of  claim 9  wherein the crank is attached to the roll bar by a universal joint. 
     
     
       11. The roll tarp system of  claim 8  wherein the means for rolling the roll bar is an electric motor. 
     
     
       12. The roll tarp system of  claim 8  further comprising means for pivotably mounting an end of at least one of the springs to the vehicle or container. 
     
     
       13. The roll tarp system of  claim 12  wherein said means comprise a hinge. 
     
     
       14. The roll tarp system of  claim 8  wherein the first reel is located near an end of the roll bar, and further comprising: 
       a second reel, the second reel being attached to the roll bar near the other end thereof; and,  
       a second constant force spring adapted for winding on the second reel, the spring having length approximately matching the widthwise dimension of the opening, the spring being attached at one end to the second reel and at the other end to the vehicle or container;  
       whereby rolling the roll bar will wind the second spring on the second reel.  
     
     
       15. The roll tarp system of  claim 14  further comprising: 
       a third reel, the third reel being attached to the roll bar near the end where the means for rolling is located; and,  
       a third constant force spring adapted for rolling on the third reel, the third spring having length approximately matching the widthwise dimension of the opening, the third spring being attached at one end to the third reel and at the other end to the vehicle or container;  
       whereby rolling of the roll bar will wind the third spring on the third reel.  
     
     
       16. A roll tarp system for reversibly covering an open top of a vehicle or container, the roll tarp system including a roll bar having first and second ends, a flexible material approximately matching-the dimensions of the opening, the flexible material attached along one longitudinal side to the roll bar and along another longitudinal side to the vehicle or container, and means for rolling the roll bar attached to the first end of the roll bar to roll the roll bar along the opening of the vehicle or container, thereby to wind and unwind the flexible material on the roll bar, the improvement comprising: 
       a reel attached near an end of the roll bar; and,  
       a constant force spring having length approximately matching the widthwise dimension of the opening and adapted to be wound upon the reel, the spring attached at one end to the reel and at the other end by mounting means to the vehicle or container;  
       whereby rolling the roll bar in one direction will wind the spring on the reel and rolling the roll bar in the opposite direction will unwind the spring from the reel.  
     
     
       17. The roll tarp system of  claim 16  wherein the means for rolling the roll bar is an electric motor and the reel is attached to the first end of the roll bar. 
     
     
       18. The roll tarp system of  claim 16  further comprising; 
       a second reel attached near an end of the roll bar; and,  
       a second constant force spring having length approximately matching the widthwise dimension of the opening and adapted to be wound upon the second reel, the second spring attached at one end to the second reel and at the other end to the vehicle or container.  
     
     
       19. The roll tarp system of  claim 18  further comprising; 
       a third reel attached near an end of the roll bar; and,  
       a third constant force spring having length approximately matching the widthwise dimension of the opening and adapted to be wound upon the third reel, the third spring attached at one end to the third reel and at the other end to the vehicle or container;  
       wherein the third reel is located near the second end of the roll bar.  
     
     
       20. The roll tarp system of  claim 16  wherein said mounting means comprises a hinge attached between the spring and the container. 
     
     
       21. The roll tarp system of  claim 20  wherein said hinge comprises a first plate portion mounted to said container, and a second plate portion pivotably attached to said first plate portion, an end of said spring being fixedly secured to said second plate portion. 
     
     
       22. The roll tarp system of  claim 20  wherein said hinge comprises a pivoting bracket slidably mounted in at least one stationary bracket, an end of said spring being fixedly secured to said pivoting bracket. 
     
     
       23. The roll tarp system of  claim 16  wherein said mounting means comprises means for directly mounting an end of said spring to said container, said system further comprising a corner track means mounted at the corner of the top and side of the container, to facilitate winding and unwinding of said spring at said corner.